Universal Mobile Telecommunication System UMTS is being developed to offer wireless wideband multimedia services. However streaming is also applicable to GSM, even though with a lower bandwidth. Images, voice, audio and video content are examples of mobile multimedia services, which are delivered to clients via media streaming and download techniques. It means once the content has been put onto a media server, it can be delivered on-demand via download or streaming. To download content, the user clicks for example on a link and waits for the content to be downloaded and playback to begin. Content streaming is done towards a single user by means of a unicast connection, when the user has requested this. The unicast connection is also called point-to-point communication.
Multicast is a service that permits sources to send a single copy of the same data to an address that causes the data to be delivered to multiple recipients. With multicast only a single copy of a data item passes over any link in a network and copies of the data item are made only where paths diverge. From the network perspective, multicast dramatically reduces overall bandwidth consumption, since the data is replicated in the network at appropriate points rather than in the end-systems. Furthermore, a server that uses multicast to distribute the content to multiple receivers, must manage only one session.
Local area networks have supported multicasting for many years. For networks, where nodes share a common communication medium multicasting is easy to support. A specially addressed packet can be read off the communication medium by multiple hosts.
Multicasting in the internetworking between a fixed network, like for example the Internet or any other IP-based backbone network and a mobile network like, General Packet Radio System GPRS or Universal Mobile Telecommunication System UMTS is currently developed, because especially in the wireless network new challenges occur. These challenges are for example the mobility of the end users and low transmission bandwidth of the mobile network on the air interface, but also the lower reliability due to the packet loss on the radio interface compared to the fixed networks.
The currently discussed multicast/broadcast integration into UMTS and GSM is depicted in FIG. 1, which shows the architecture of multimedia broadcast/multicast. In FIG. 1 the most relevant nodes of GPRS or UMTS network and examples of the different access networks, like UTRAN and GERAN, are presented. The access networks are handled by means of a serving node, SGSN that communicates with an edge node, the GGSN that is responsible for connection to the external networks, like Internet. The BM-SC entity is responsible for the provision of multicast/broadcast, like for example for bearer establishment and data forwarding. However there is currently no solution existing, which works for multicasting of streaming. Since the idea is that the current BM-SC proposals simply forward the content. The functionality for handling a streaming flow is not included in the BM-SC.
Currently the signalling and transmission of the streaming flow for a single user is performed in a wireless network by means of a Packet Switched Streaming architecture, which has a streaming server distributing the streaming flow to a streaming node, which can be realised by means of network integration nodes NINs. There are also solution, in which a content servers distributes the streaming content directly to the streaming clients on the user's side. These content servers are either the streaming servers or the NINs. The streaming nodes communicate with the GGSN that forwards the stream to the SGSN and then via the radio network to a user.
Simply aggregating both solutions would lead to a system in which a streaming session is established for every user interested in receiving the streaming flow, implying that such a service will be very inefficiently deployed, especially in wireless networks, since it does not utilize the scarce radio resources in an optimal way. Furthermore although the transport may be multicast, a separate streaming session would be established per client with dedicated on-demand signalling messages. Further the adaptation will be done for the whole group and not on a per subgroup base, implying that the adaptation is general and not optimized for the different subgroups. Currently an individual adaptation can be achieved because all users have a separate and dedicated streaming session, wherein this solution leads to wasting of network resources.
Therefore currently there is no integration between the multicast and the unicast streaming transmission, providing an efficient and effective solution.